Froth flotation is commonly used in the mining industry to recover mineral values from aqueous ore slurries. A wide variety of suitable frothing agents have been identified, although the best frother for a particular application is usually selected through experience or by trial and error. Alkyl or aryl ethers of propylene glycol and polypropylene is glycols have long been generally known as effective frothing agents for copper recovery (see, e.g., U.S. Pat. Nos. 2,611,485, 2,695,101, and 3,595,390).
The South African mining industry uses tripropylene glycol methyl ether (TPM) as a frothing agent for recovering platinum and other precious metals. While the product performs well, it is produced commercially as a by-product of the normal process for making propylene glycol methyl ether (PM) from methanol and propylene oxide. Consequently, TPM is expensive and in relatively short supply. Unfortunately, demand for TPM is still not sufficient to justify its “on purpose” manufacture.
The mining industry, particularly the platinum mining industry, would benefit from the availability of inexpensive alternatives to TPM that provide acceptable performance as frothing agents. Not all alkylene glycol ether compositions are suitable for use in platinum recovery. For example, our own evaluation of ethoxylated PM demonstrated unacceptable frothing performance.